Dc-dc converter and manufacturing method thereof

Abstract

A DC-DC converter is driven by single high input voltage, and includes a voltage converter circuit and a control circuit. The increase of the occupied area of the DC-DC converter is suppressed. The DC-DC converter includes an input terminal to which input voltage is applied; a voltage converter circuit connected to the input terminal, and including a first transistor; a control circuit configured to control the voltage converter circuit, and including a second transistor including a silicon material in a channel formation region; and a third transistor provided between the input terminal and the control circuit, and configured to convert the input voltage into power supply voltage that is lower than the input voltage. The first transistor and the third transistor include an oxide semiconductor material in channel formation regions. The first transistor and the third transistor are stacked over the second transistor with an insulating film provided therebetween.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]One embodiment of the disclosed invention relates to a DC-DC converter and a manufacturing method thereof.[0003]2. Description of the Related Art[0004]In recent years, DC-DC converters have been widely used in order to drive circuits which are driven by DC voltage that is different from input voltage because devices which need DC voltage sources have been diversified (see Patent Document 1, Patent Document 2, and Patent Document 3).[Reference][0005][Patent Document 1] Japanese Published Patent Application No. 2009-148129[0006][Patent Document 2] Japanese Published Patent Application No. 2003-235251[0007][Patent Document 3] Japanese Published Patent Application No. 2009-254110SUMMARY OF THE INVENTION[0008]A DC-DC converter includes a voltage converter circuit and a control circuit which controls the voltage converter circuit. A power device which has high breakdown voltage is used for an element of the voltage converter ...

AI Technical Summary

Benefits of technology

[0012]Therefore, an element which decreases high input voltage is provided between an input terminal to which the high input voltage is applied and the control circuit. When the decreased voltage is supplied to the control circuit, there is no risk of breaking the control circuit.

[0030]In one embodiment of the disclosed invention, the number of manufacturing steps and manufacture cost can be decreased because a power device of a voltage converter circuit and a power device which decreases input voltage are formed in the same process.

Problems solved by technology

However, high voltage cannot be applied to the element using a silicon material because the element does not have high breakdown voltage.

Since silicon has a narrow band gap, an avalanche breakdown in which electrons are generated like an avalanche might occur.

However, although the high input voltage can drive the voltage converter circuit, the high input voltage might break the control circuit because it is too high as the voltage of the control circuit.

Accordingly, it is difficult to drive the DC-DC converter having a voltage converter circuit and a control circuit only by the single high input voltage.

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